Evaporator for refrigeration systems

ABSTRACT

An evaporator for refrigeration systems, comprising a set of tubes ( 20 ) arranged in series, spaced and parallel in relation to each other, carrying a refrigerant fluid and which are incorporated to and trespass a plurality of fins ( 10 ) arranged in multiple rows extending transversally to the direction of a forced airflow (F). The fins ( 10 ), which are incorporated to the first and second tubes ( 20 ) are spaced from each other by a larger distance (d), when they are operatively associated with a refrigerating environment, and by a smaller distance (d), when they are operatively associated with a freezing environment. Said distances (d) decrease at each two subsequent tubes ( 20 ), until reaching at least the third tube ( 20 ), said distance being then maintained at a minimum value for the other subsequent tubes ( 20 ).

FIELD OF THE INVENTION

The present invention refers to the construction of an evaporator forrefrigeration systems, more particularly to the arrangement of the finsof an evaporator of the tube-fin type for refrigeration systems withforced ventilation, generally used in refrigerators, freezers and otherrefrigeration appliances.

BACKGROUND OF THE INVENTION

The refrigeration systems with forced ventilation usually applied torefrigerators and freezers, generally use a compact evaporator of thetube-fin type comprising a plurality of fins incorporated to andtrespassed by a set of tubes arranged in series in the form of a coiland carrying a refrigerant fluid. A forced airflow is forced to passthrough the evaporator, which airflow is drawn from the inside of anenvironment to be cooled, in order to be refrigerated by the evaporatorand discharged back to the interior of said environment, as it occursfor example in the refrigerating or freezing compartments of arefrigeration appliance.

These evaporators are constructed to assure a certain acceptable degreeof thermal exchange between the forced airflow that is forced to passover the tubes of the evaporator and over the fins orthogonally affixedto said tubes. However, since the heated air to be forced through theevaporator contains humidity in a higher or lower degree as a functionof the operation to which the environment to be refrigerated issubmitted, this humidity tends to condensate, causing the formation ofice in the evaporator.

The formation of ice occurs in a non-uniform way in the evaporator, withthe ice accumulating more intensively on the leading edge of the finsand the tube, that is, at the region in which the airflow enters intothe evaporator, restraining the airflow cross section between the fins.

Aiming at maintaining an adequate performance of the evaporator duringthe operation of the refrigeration system to which it is coupled, it isnecessary to periodically remove, with a certain frequency, the iceaccumulated in the evaporator. The defrost operations are usuallyautomatically effected by the control system of the refrigerationappliance, generally a refrigerator, freezer, or a combined appliancewith both functions.

The evaporators of the tube-fin type considered herein have beendeveloped with the purpose of enhancing the heat transfer, increasingthe thermal efficiency and allowing the use of more compact componentsof lower cost.

Following the evolutional process, the evaporator E had the fins 10thereof modified, from a continuous form, as illustrated in FIG. 1 ofthe attached drawings, extending along the length of the evaporatoraccording to the direction of the forced airflow path, to an interruptedform defined by fins that are mutually spaced, not only transversally tothe direction of the forced airflow path, but also longitudinally alongthe length of the evaporator, as illustrated in FIG. 2 of the drawings,making the fins 10 be longitudinally arranged in rows that aretransversal to the direction of the airflow path, with the fins 10 ofeach row being mutually parallel and spaced.

With the objective of imparting more capacity to the evaporator E tooperate with the non-uniform pattern of ice formation, but allowing anoperation that continues to comply with the requirements of thermalexchange efficiency, a constructive arrangement is usually employed,according to which the spacing between the fins 10 of the same rowdecreases from the first row of fins 10 provided close to the air inletregion of the evaporator E, to the last row of fins 10 provided close tothe air outlet region of the evaporator, as illustrated in FIG. 2, whichalso shows, in a simple way, the non-uniform formation of ice G on thefins 10 and tubes 20 of the evaporator E. Nevertheless, the knowndecreasing variation of the spacing between the fins 10 of each row can,as a function of the distribution flexibility made possible, lead todifferent evaporator configurations, which are constructed either toincrease the thermal exchange efficiency to the detriment of thecapacity of the evaporator to operate with a certain degree of iceformation, or to increase said capacity to the detriment of the thermalefficiency of the evaporator E.

FIG. 3 of the enclosed drawings illustrates, schematically andpartially, an arrangement of fins 10, in which the spacing therebetweenhas been calculated to increase the thermal exchange efficiency, to thedetriment of the capacity to operatively support a certain degree offormation of ice G. The formation of ice G tends to prematurely obstructthe passage of the forced airflow through the evaporator.

FIG. 4, similarly to FIG. 3, illustrates an arrangement of fins 10, inwhich the spacing therebetween aimed at increasing the capacity of theevaporator to operate with the formation of ice G, to the detriment ofthe thermal exchange efficiency. The result of this arrangement is theprovision of an evaporator that requires less frequent defrostoperations, but which operates with low efficiency in terms of heattransfer.

OBJECT OF THE INVENTION

It is the object of the present invention to provide an evaporator ofthe tube-fin type for refrigeration systems with forced ventilation,presenting a fin distribution which allows optimizing the compromisebetween the capacity of thermal exchange with a forced airflow that isforced to pass through the evaporator, and the capacity of saidevaporator to operate with the formation of ice and thus maximize itsthermal performance.

SUMMARY OF THE INVENTION

According to the general object mentioned above, the present inventionis applied to an evaporator to be used in refrigeration systems ofrefrigerators, freezers, combined appliances, and other refrigerationappliances. The present evaporator is of the type that comprises a setof tubes arranged in series, spaced and parallel in relation to eachother, carrying a refrigerant fluid and which are incorporated to andtrespass a plurality of fins arranged in multiple rows extendingtransversally to the direction of a forced airflow that is forced topass through the evaporator and through an environment to berefrigerated, each row being formed by a plurality of fins arrangedsubstantially parallel to the direction of the forced airflow andincorporated to at least one of said tubes.

According to the invention, the fins 10, which are incorporated to thefirst and second tubes 20, according to the direction of the forced airflow F, are spaced from each other by a larger distance d, when they areoperatively associated with a refrigerating environment, and by asmaller distance d, when they are operatively associated with a freezingenvironment. Said distances d decrease at each two subsequent tubes 20,until reaching at least the third tube 20, said distance being thenmaintained at a minimum value for the other subsequent tubes 20. Theconstructive arrangement proposed by the present invention allowsobtaining an optimum coefficient of thermal exchange for the evaporator,which can have its fins arranged to operate with forced airflowscirculating through different environments to be refrigerated, with thearrangement being made so that a higher level of ice formation in theevaporator region is supported without significantly affecting thethermal exchange efficiency.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be described below, with reference to the attacheddrawings, in which:

FIG. 1 is a somewhat schematic front view of a prior art evaporator ofthe tube-fin type, with each fin being constructed in a singlecontinuous piece incorporated transversally to all the tubes of theevaporator and trespassed by said tubes;

FIG. 2 is a similar view to that of FIG. 1, but illustrating a prior artfin-tube evaporator, with the fins arranged in rows transversally to theforced airflow, each row being incorporated to a respective pair ofadjacent tubes;

FIGS. 3-4 are schematic views of arrangements of fins disposed in rows,according to prior art arrangements, illustrating the formation of ice,when priority is given to the thermal exchange efficiency and whenpriority is given to the resistance to ice formation, respectively;

FIG. 5 is a schematic front view of an evaporator of the fin-tub type,serving both a refrigerating environment and a freezing environment, andhaving the fins arranged according to a first embodiment of theinvention; and

FIG. 6 is a view similar to that of the previous figure, butillustrating the fins arranged according to another embodiment of theinvention.

DESCRIPTION OF THE ILLUSTRATED EMBODIMENTS

As illustrated in FIGS. 1 and 6, the evaporator E of the presentinvention comprises a plurality of fins 10 arranged in multiple rows,extending transversally to the direction of a forced airflow F that isforced to pass through the evaporator E, as well as through one or moreenvironments to be refrigerated (not illustrated) and which can bedefined, for example, by a refrigerating environment, such as thecompartment of a refrigerator, which is refrigerated at a temperature ofabout 5° C. to about 0° C., and by a freezing environment, such as thecompartment of a freezer, which is refrigerated at a temperature ofabout −10° C. to about −20° C.

The forced airflow F is produced by a fan (not illustrated), which isadequately mounted in series with the air circulation to be producedthrough the evaporator and through the respective environment(s) to berefrigerated.

The fins 10 are obtained from a plate made of a material of high thermalconductivity, with a thickness generally of about 0.1-0.2 mm andpresenting a rectilinear embodiment.

In the illustrated embodiments, the fins 10 have the same dimensions andare arranged in rectilinear alignments in each row, with the rows beingspaced from each other by a spacing “a”, which will be better definedbelow.

As illustrated, the evaporator E further comprises a set of tubes 20arranged in series, spaced from and parallel to each other, carrying arefrigerant fluid and which are incorporated to the fins 10, trespassingthem orthogonally.

In the constructions illustrated in FIGS. 5 and 6, each row of fins 10is incorporated to a respective pair of adjacent tubes 20, however itshould be understood that each row of fins 10 can be incorporated to asingle tube 20.

According to the invention, the fins 10 incorporated to the first andsecond tubes 20, taking in consideration the direction of the forcedairflow F, are spaced from each other by a distance “d” that varies from3X to 4X, when they are operatively associated with a refrigeratingenvironment, with the constant “X” ranging from 4 to 7 mm. This is thecondition for the mutual distance of the fins 10 provided at the inletregion of the forced airflow F in the evaporator E and incorporated tothe first and second tubes 20, when these fins 10 are operativelyassociated with a refrigerator compartment (refrigerating environment),whose air contains a higher amount of humidity which will form the ice Gmore intensively at the inlet region of the evaporator E.

In case the fins 10 are operatively associated with a freezingenvironment, such as a freezer compartment, with a lower amount ofhumidity in the circulating air, the distance “d” between the fins 10incorporated to the first and second tubes 20 varies from 2X to 3X, thatis, it is maintained slightly smaller than that applied to the same fins10 operating with the forced airflow coming from a refrigeratingenvironment.

In the constructions illustrated in FIGS. 5 and 6, the evaporator E isconstructed to operate simultaneously with a refrigerating environmentand with a freezing environment, which situation is common at thecombined refrigeration appliances that comprise a refrigeratingcompartment and a freezing compartment.

In this type of construction, the evaporator E presents its fins 10arranged in a set of fins, occupying a cross section area correspondingto the cross section area of a respective duct DR and DC for the returnof the forced airflow F from the environment to be refrigerated andoperatively associated with said set of fins 10 that follows arespective pattern of mutual distance. In the illustrated examples, thecentral fins 10 are arranged to operate with the forced airflow comingfrom a refrigerating environment through a duct DR, while the lateralfins 10 are arranged to operate with the forced airflow coming from afreezing environment through respective sections of the duct DC.

According to the direction of the forced airflow F that is forced topass through the evaporator E, the distance “d” between the fins 10subsequent to those incorporated to the first and second tubes 20decreases at each two subsequent tubes 20, until reaching at least thethird tube 20, said distance being then maintained with the value “X”,until reaching the last tube 20.

For the fins 10 operatively associated with the refrigeratingenvironment, the distance “d” decreases by a value corresponding to “X”from each two adjacent tubes 20 to the two subsequent tubes 20. However,for the fins 10 operatively associated with the freezing environment,said decrease of the distance “d” is made by values corresponding to X/2for the lower limit, and from X/2 to X for the upper limit. Preferably,the upper limit for the decrease of the distance “d” between the fins 10operatively associated with the freezing environment is X between thefins 10 incorporated to the first and second tubes 20 and thoseincorporated to the third and fourth tubes 20, and X/2 from these lastfins 10 to those incorporated to each of the other pairs of subsequenttubes 20, until reaching the minimum distance “X” that will bemaintained until reaching the fins 10 incorporated to the last tube 20,close to the outlet region of the forced airflow F of the evaporator E.

Still according to the invention, the spacing “a” between each twoconsecutive rows of fins 10 varies from X/3 to X/2, preferably being ofabout 1.75 mm, and the adjacent rows, which present the same distance“d” between the fins 10, have their fins 10 preferably andlongitudinally offset in relation to the fins of the adjacent rows, inorder to increase the contact of the mass of the forced airflow Ftherewith in a region of the evaporator E that is subject to a reduceddegree of formation of ice G.

In the embodiment shown in FIG. 5, the distance “d” between the fins 10operatively associated with the refrigerating environment, that is,between the fins 10 associated with the central duct DR, is preferablyof about 15 mm for the fins incorporated to the first and second tubes20, about 10 mm for the fins 10 incorporated to the third and fourthtubes 20, about 7.5 mm for the fins 10 incorporated to the fifth andsixth tubes 20, and about 5 mm for the fins 10 incorporated to the othertubes 20 of the evaporator E.

For the fins 10 operatively associated with the freezing environment,that is, the fins 10 associated with the lateral ducts DC, the distance“d” is preferably of about 10 mm for the fins 10 incorporated to thefirst and second tubes 20, and about 7.5 mm for the fins 10 incorporatedto the third, fourth, fifth and sixth tubes 20, and of about 5 mm forthe fins 10 incorporated to the other tubes 20.

In the embodiment of FIG. 5, the distance “d” between the fins 10operatively associated with the refrigerating environment is decreasedat each consecutive pair of tubes 20 until reaching the seventh tube 20,while the distance “d” between the fins 10 operatively associated withthe freezing environment is decreased only from the second tube 20 tothe third tube 20, and from the sixth tube 20 to the seventh tube 20.

In the embodiment of FIG. 6, the distance “d” between the fins 10operatively associated with the refrigerating environment is preferablyof about 15 mm for the fins 10 incorporated to the first and secondtubes 10, about 10 mm for the fins 10 incorporated to the third andfourth tubes 20, and of about 5 mm for the fins 10 incorporated to theother tubes 20. For the fins 10 operatively associated with the freezingenvironment, the distance “d” is preferably of about 10 mm for the fins10 incorporated to the first, second, third and fourth tubes 20, and ofabout 5 mm for the fins 10 incorporated to the other tubes 20.

The constructive arrangement described above allows for the fins to bemutually spaced, as a function of the characteristics of the airflowthat is forced to pass therethrough, and as a function of theirpositioning along the longitudinal extension of the evaporator, allowingboth the thermal exchange efficiency and the operational resistance toice formation to be simultaneously optimized.

1. An evaporator for refrigeration systems, comprising a set of tubes(20) arranged in series, spaced and parallel in relation to each other,carrying a refrigerant fluid and which are incorporated to and trespassa plurality of fins (10) arranged in multiple rows and extendingtransversally to the direction of a forced airflow (F) that is forced topass through the evaporator (E) and through an environment to berefrigerated, each row being formed by a plurality of fins (10) arrangedsubstantially parallel to the direction of the forced airflow (F) andincorporated to at least one of said tubes (20), characterized in thatthe fins (10), which are incorporated to the first and second tubes (20)according to the direction of the forced air flow (F), are spaced fromeach other by a larger distance (d), when they are operativelyassociated with a refrigerating environment, and by a smaller distance(d), when they are operatively associated with a freezing environment,said distances (d) decreasing at each two subsequent tubes (20), untilreaching at least the third tube (20), said distance being thenmaintained at a minimum value for the other subsequent tubes (20). 2.The evaporator as set forth in claim 1, characterized in that saiddistance (d) between the fins (10) incorporated to the first and secondtubes (20) varies from 3X to 4X for the fins (10) operatively associatedwith the refrigerating environment, and from 2X to 3X for the fins (10)operatively associated with the freezing environment, the constant “X”varying from 4 to 7 mm, and the limits for the variation of the distance(d) between the fins (10) associated with each two adjacent tubes (20)decreasing for the two subsequent tubes (20) by a value corresponding to“X” for the fins (10) operatively associated with the refrigeratingenvironment, and corresponding to X/2 for the lower limit, and from X/2to X for the upper limit for the fins (10) operatively associated withthe freezing environment, said decrease of the distance (d) occurringuntil reaching the value “X”, which is maintained for the othersubsequent tubes (20), the spacing (a) between the rows of fins (10)varying from X/3 to X2.
 3. The evaporator as set forth in claim 1,characterized in that the fins (10) of each row have the samedimensions.
 4. The evaporator as set forth in claim 3, characterized inthat the fins (10) of each row are arranged according to rectilinearalignments.
 5. The evaporator as set forth in claim 1, characterized inthat the fins (10) of each row are incorporated to a respective pair ofadjacent tubes (20).
 6. The evaporator as set forth in claim 1, which issimultaneously and operatively associated with a refrigeratingenvironment and with a freezing environment, characterized in that eachrow presenting the fins (10) mutually spaced by a distance (d) largerthan “X” comprises a set of fins (10) occupying a cross section areacorresponding to the cross section area of a respective duct (DR, DC)for the return of the forced airflow (F) from the environment to berefrigerated and operatively associated with said set of fins (10), thedistance (d) between the latter being dimensioned as a function of thecharacteristics of the refrigeration to be imparted to the respectiveenvironment to be refrigerated by the respective set of fins (10). 7.The evaporator as set forth in claim 1, characterized in that thedistance (d) between the fins (10), which are operatively associatedwith the refrigerating environment, is of about 15 mm for the fins (10)incorporated to the first and to the second tubes (20), of about 10 mmfor the fins (10) incorporated to the third and to the fourth tubes(20), about 7.5 mm for the fins (10) incorporated to the fifth and tothe sixth tubes (20), and of about 5 mm for the fins (10) incorporatedto the other tubes (20) of the evaporator (E).
 8. The evaporator as setforth in claim 1, characterized in that the distance (d) between thefins (10), which are operatively associated with the freezingenvironment, is of about 10 mm for the fins (10) incorporated to thefirst and second tubes (20), and of about 7.5 mm for the fins (10)incorporated to the third, fourth, fifth, and sixth tubes (20), and ofabout 5 mm for the fins (10) incorporated to the other tubes (20). 9.The evaporator as set forth in claim 1, characterized in that thedistance (d) between the fins (10), which are operatively associatedwith the refrigerating environment, is of about 15 mm for the fins (10)incorporated to the first and second tubes (20), about 10 mm for thefins (10) incorporated to the third and fourth tubes (20), and of about5 mm for the fins (10) incorporated to the other tubes (20).
 10. Theevaporator as set forth in claim 1, characterized in that the distance(d) between the fins (10), which are operatively associated with thefreezing environment is of about 10 mm for the fins (10) incorporated tothe first, second, third, and fourth tubes (20), and of about 5 mm forthe fins (10) incorporated to the other tubes (20).
 11. The evaporatoras set forth in claim 1, characterized in that the adjacent rowspresenting the same distance (d) between the fins (10) have their fins(10) longitudinally offset in relation to the fins (10) of the adjacentrows.
 12. The evaporator as set forth in claim 1, characterized in thatthe rows of fins (10) maintain a spacing (a) of about 1.75 mm from eachother.